In a combustion-powered tool, such as, for example a fastener-driving tool of a type exemplified in Nikolich U.S. Pat. Nos. 4,403,722, 4,483,474, and Re. 32,452, it is known to add a lubricating oil to a hydrocarbon fuel, which combust so as to drive the tool. As exemplified in these patents, electromechanical switches are used within such tools. Although photoelectric switches of the type wherein a shutter is used to selectively block and unblock a line of sight defined between a phototransmissive device and a photoreceptive device would be more reliable within such a tool, in which shocks and vibrations tend to be frequently encountered, it has not been known heretofore to use such photoelectric switches within such tools.
Within such a tool, oil mist, combustion products, or both are pervasive and would militate against the usage of photoelectric switches of the type noted above, since the infiltration of oil mist or other contaminants would tend to interfere with the proper operation of such a switch. There has been a need, to which this invention is addressed, for a photoelectric switch of the type noted above that is sealed against the infiltration of contaminants, such as, for example oil mist, which could interfere with its proper operation.